Drool

Ivan Pavlov’s real quest.

Pavlov (operating on a dog in 1902) ran his lab like a factory; dogs were his machines.

Courtesy Wellcome Library, London

As a college student, B. F. Skinner gave little thought to psychology. He had hoped to become a novelist, and majored in English. Then, in 1927, when he was twenty-three, he read an essay by H. G. Wells about the Russian physiologist Ivan Pavlov. The piece, which appeared in the Times Magazine, was ostensibly a review of the English translation of Pavlov’s “Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex.” But, as Wells pointed out, it was “not an easy book to read,” and he didn’t spend much time on it. Instead, Wells described Pavlov, whose systematic approach to physiology had revolutionized the study of medicine, as “a star which lights the world, shining down a vista hitherto unexplored.”

That unexplored world was the mechanics of the human brain. Pavlov had noticed, in his research on the digestive system of dogs, that they drooled as soon as they saw the white lab coats of the people who fed them. They didn’t need to see, let alone taste, the food in order to react physically. Dogs naturally drooled when fed: that was, in Pavlov’s terms, an “unconditional” reflex. When they drooled in response to a sight or sound that was associated with food by mere happenstance, a “conditional reflex” (to a “conditional stimulus”) had been created. Pavlov had formulated a basic psychological principle—one that also applied to human beings—and discovered an objective way to measure how it worked.

Skinner was enthralled. Two years after reading the TimesMagazine piece, he attended a lecture that Pavlov delivered at Harvard and obtained a signed picture, which adorned his office wall for the rest of his life. Skinner and other behaviorists often spoke of their debt to Pavlov, particularly to his view that free will was an illusion, and that the study of human behavior could be reduced to the analysis of observable, quantifiable events and actions.

But Pavlov never held such views, according to “Ivan Pavlov: A Russian Life in Science” (Oxford), an exhaustive new biography by Daniel P. Todes, a professor of the history of medicine at Johns Hopkins School of Medicine. In fact, much of what we thought we knew about Pavlov has been based on bad translations and basic misconceptions. That begins with the popular image of a dog slavering at the ringing of a bell. Pavlov “never trained a dog to salivate to the sound of a bell,” Todes writes. “Indeed, the iconic bell would have proven totally useless to his real goal, which required precise control over the quality and duration of stimuli (he most frequently employed a metronome, a harmonium, a buzzer, and electric shock).”

Pavlov is perhaps best known for introducing the idea of the conditioned reflex, although Todes notes that he never used that term. It was a bad translation of the Russian uslovnyi, or “conditional,” reflex. For Pavlov, the emphasis fell on the contingent, provisional nature of the association—which enlisted other reflexes he believed to be natural and unvarying. Drawing upon the brain science of the day, Pavlov understood conditional reflexes to involve a connection between a point in the brain’s subcortex, which supported instincts, and a point in its cortex, where associations were built. Such conjectures about brain circuitry were anathema to the behaviorists, who were inclined to view the mind as a black box. Nothing mattered, in their view, that could not be observed and measured. Pavlov never subscribed to that theory, or shared their disregard for subjective experience. He considered human psychology to be “one of the last secrets of life,” and hoped that rigorous scientific inquiry could illuminate “the mechanism and vital meaning of that which most occupied Man—our consciousness and its torments.” Of course, the inquiry had to start somewhere. Pavlov believed that it started with data, and he found that data in the saliva of dogs.

Pavlov’s research originally had little to do with psychology; it focussed on the ways in which eating excited salivary, gastric, and pancreatic secretions. To do that, he developed a system of “sham” feeding. Pavlov would remove a dog’s esophagus and create an opening, a fistula, in the animal’s throat, so that, no matter how much the dog ate, the food would fall out and never make it to the stomach. By creating additional fistulas along the digestive system and collecting the various secretions, he could measure their quantity and chemical properties in great detail. That research won him the 1904 Nobel Prize in Physiology or Medicine. But a dog’s drool turned out to be even more meaningful than he had first imagined: it pointed to a new way to study the mind, learning, and human behavior.

“Essentially, only one thing in life is of real interest to us—our psychical experience,” he said in his Nobel address. “Its mechanism, however, was and still is shrouded in profound obscurity. All human resources—art, religion, literature, philosophy, and the historical sciences—all have joined in the attempt to throw light upon this darkness. But humanity has at its disposal yet another powerful resource—natural science with its strict objective methods.”

Pavlov had become a spokesman for the scientific method, but he was not averse to generalizing from his results. “That which I see in dogs,” he told a journalist, “I immediately transfer to myself, since, you know, the basics are identical.”

Ivan Pavlov was born in 1849 in the provincial Russian city of Ryazan, the first of ten children. As the son of a priest, he attended church schools and the theological seminary. But he struggled with religion from an early age and, in 1869, left the seminary to study physiology and chemistry at St. Petersburg University. His father was furious, but Pavlov was undeterred. He never felt comfortable with his parents—or, as this biography makes clear, with almost anyone else. Not long after “The Brothers Karamazov” was published, Pavlov confessed to his future wife, Seraphima Vasilievna Karchevskaya, who was a friend of Dostoyevsky’s, that he identified with the rationalist Ivan Karamazov, whose brutal skepticism condemned him, as Todes notes, to nihilism and breakdown. “The more I read, the more uneasy my heart became,” Pavlov wrote in a letter to Karchevskaya. “Say what you will, but he bears a great resemblance to your tender and loving admirer.”

Pavlov entered the intellectual world of St. Petersburg at an ideal moment for a man eager to explore the rules that govern the material world. The tsar had freed the serfs in 1861, helping to push Russia into the convulsive century that followed. Darwin’s theory of evolution was starting to reverberate across Europe. Science began to matter in Russia in a way it hadn’t before. At the university, Pavlov’s freshman class in inorganic chemistry was taught by Dmitri Mendeleev, who, a year earlier, had created the periodic table of the elements as a teaching tool. The Soviets would soon assign religion to the dustbin of history, but Pavlov got there ahead of them. For him, there was no religion except the truth. “It is for me a kind of God, before whom I reveal everything, before whom I discard wretched worldly vanity,” he wrote. “I always think to base my virtue, my pride, upon the attempt, the wish for truth, even if I cannot attain it.” One day, while walking to his lab at the Institute for Experimental Medicine, Pavlov watched with amazement as a medical student stopped in front of a church and crossed himself. “Think about it!” Pavlov told his colleagues. “A naturalist, a physician, but he prays like an old woman in an almshouse!”

Pavlov was not a pleasant person. Todes presents him as a volatile child, a difficult student, and, frequently, a nasty adult. For decades, his lab staff knew to stay away, if at all possible, on his “angry days,” and there were many. As a member of the liberal intelligentsia, he was opposed to restrictive measures aimed at Jews, but in his personal life he freely voiced anti-Semitic sentiments. Pavlov once referred to “that vile yid, Trotsky,” and, when complaining about the Bolsheviks in 1928, he told W. Horsley Gantt, an American scientist who spent years in his lab, that Jews occupied “high positions everywhere,” and that it was “a shame that the Russians cannot be rulers of their own land.”

In lectures, Pavlov insisted that medicine had to be grounded in science, on data that could be explained, verified, and analyzed, and on studies that could be repeated. Drumming up support among physicians for the scientific method may seem banal today, but at the end of the nineteenth century it wasn’t an easy sell. In Russia, and even to some degree in the West, physiology was still considered a “theoretical science,” and the connection between basic research and medical treatments seemed tenuous. Todes argues that Pavlov’s devotion to repeated experimentation was bolstered by the model of the factory, which had special significance in a belatedly industrializing Russia. Pavlov’s lab was essentially a physiology factory, and the dogs were his machines.

To study them, he introduced a rigorous experimental approach that helped transform medical research. He recognized that meaningful changes in physiology could be assessed only over time. Rather than experiment on an animal once and then kill it, as was common, Pavlov needed to keep his dogs alive. He referred to these studies as “chronic experiments.” They typically involved surgery. “During chronic experiments, when the animal, having recovered from its operation, is under lengthy observation, the dog is irreplaceable,” he noted in 1893.

The dogs may have been irreplaceable, but their treatment would undoubtedly cause an outcry today. Todes writes that in early experiments Pavlov was constantly stymied by the difficulty of keeping his subjects alive after operating on them. One particularly productive dog had evidently set a record by producing active pancreatic juice for ten days before dying. The loss was a tremendous disappointment to Pavlov. “Our passionate desire to extend experimental trials on such a rare animal was foiled by its death as a result of extended starvation and a series of wounds,” Pavlov wrote at the time. As a result, “the expected resolution of many important and controversial questions” had been delayed, awaiting another champion test subject.

If Pavlov’s notes were voluminous, Todes’s own investigations are hardly modest. He spent years researching this biography and has made excellent use of archives in Russia, Europe, and the United States. No scholar of Pavlov or of the disciplines he inspired will be able to ignore this achievement. The book’s eight hundred and fifty-five pages are filled with a vast accumulation of data, although the reader might have been better served if Todes had left some of it out. No minutia appears to have been too obscure to include. Here is Todes describing data that Pavlov had assembled from one extended experiment: “The total amount of secretion in trials 6 and 8 is too low, and the slope of these curves diverges markedly at several points from that in trial 1. Trial 9 fits trial 1 more snugly than does trial 5 in terms of total secretion, but the amount of secretion more than doubles in the second hour, contrasting sharply with the slight decline in trial 1. Trial 10 is again a good fit in terms of total amount of secretion, but the amount of secretion rises inappropriately in the fourth hour.” The diligent reader can also learn, in excruciating detail, what time Pavlov took each meal during summer holidays (dinner at precisely 12:30 P.M., tea at four, and supper at eight), how many cups of tea he typically consumed each afternoon (between six and ten), and where the roses were planted in his garden (“around the spruce tree on the west side of the veranda”). It’s hard not to wish that Todes had been a bit less devoted to his subject’s prodigious empiricism.

For more than thirty years, Pavlov’s physiology factory turned out papers, new research techniques, and, of course, gastric juice—a lot of it. On a good day, a hungry dog could produce a thousand cubic centimetres, more than a quart. Although this was a sideline for Pavlov, the gastric fluids of a dog became a popular treatment for dyspepsia, and not just in Russia. A “gastric juice factory” was set up for the purpose. “An assistant was hired and paid thirty rubles a month to oversee the facility,” Todes writes. “Five large young dogs, weighing sixty to seventy pounds and selected for their voracious appetites, stood on a long table harnessed to the wooden crossbeam directly above their heads. Each was equipped with an esophagotomy and fistula from which a tube led to the collection vessel. Each ‘factory dog’ faced a short wooden stand tilted to display a large bowl of minced meat.” By 1904, the venture was selling more than three thousand flagons of gastric juice annually, Todes writes, and the profits helped increase the lab budget by about seventy per cent. The money was helpful. So was the apparent demonstration that a product created in an experimental laboratory could become useful to doctors all over the world.

At the turn of the century, Pavlov had begun focussing his research on “psychic secretions”: drool produced by anything other than direct exposure to food. He spent most of the next three decades exploring the ways conditional reflexes could be created, refined, and extinguished. Before feeding a dog, Pavlov might set a metronome at, say, sixty beats a minute. The next time the dog heard a metronome at any speed, it would salivate. But when only that particular metronome setting was reinforced with food the dog became more discriminating. Pavlov deduced that there were colliding forces of “excitation” and “inhibition” at play—so that, at first, the stimulus spreads across the cerebral cortex and then, in the second phase, it concentrates at one specific spot.

As his formulations and models grew more complex, Pavlov was encouraged in his hope that he would be able to approach psychology through physiology. “It would be stupid to reject the subjective world,” he remarked later. “Our actions, all forms of social and personal life are formed on this basis. . . . The question is how to analyze this subjective world.”

Pavlov was sixty-eight and had been famous for years when Lenin came to power, and Todes is at his best in describing the scientist’s relationship with the regime that he would serve for the rest of his life. Pavlov harbored no sentimental attachment to the old order, which had never been aggressive in funding scientific research. The Bolsheviks promised to do better (and, eventually, they did). Yet Pavlov considered Communism a “doomed” experiment that had turned Russia back into a nation of serfs. “Of course, in the struggle between labor and capital the government must stand for the protection of the worker,” he said in a speech. “But what have we made of this? . . . That which constitutes the culture, the intellectual strength of the nation, has been devalued, and that which for now remains a crude force, replaceable by a machine, has been moved to the forefront. All this, of course, is doomed to destruction as a blind rejection of reality.”

Lenin had too many other problems to spend his time worrying about one angry scientist. At first, Pavlov, his wife, and their four children were treated like any other Soviet citizens. Their Nobel Prize money was confiscated as property of the state. From 1917 to 1920, like most residents of Petrograd, which would soon be called Leningrad, the Pavlovs struggled to feed themselves and to keep from freezing. It was nearly a full-time occupation; at least a third of Pavlov’s colleagues at the Russian Academy of Sciences died in those first post-revolutionary years. “Some starved to death in apartments just above or below his own in the Academy’s residence,” Todes writes. Pavlov grew potatoes and other vegetables right outside his lab, and when he was sick a colleague provided small amounts of firewood to burn at home.

In 1920, Pavlov wrote to Lenin’s secretary, Vladimir Bonch-Bruevich, seeking permission to emigrate, although, as Todes points out, it was probably not yet necessary to ask. Pavlov wanted to see if, as he suspected, universities in Europe or America would fund his research in circumstances that would prevent his dogs and lab workers from starving. Bonch-Bruevich turned the letter over to Lenin, who immediately grasped the public-relations repercussions of losing the country’s most celebrated scientist. He instructed Petrograd Party leaders to increase rations for Pavlov and his family, and to make sure his working conditions improved.

The Soviets came to regard Pavlov as a scientific version of Marx. The comparison could not entirely have pleased Pavlov, who rebelled at the “divine” authority accorded Marx (“that fool”) and denied that his own “approach represents pure materialism.” Indeed, where others thought that the notion of free will would come to be discarded once we had a full understanding of how the mind worked, Pavlov was, at least at times, inclined to think the opposite. “We would have freedom of the will in proportion to our knowledge of the brain,” he told Gantt in 1927, just as “we had passed from a position of slave to a lord of nature.”

That year, Stalin began a purge of intellectuals. Pavlov was outraged. At a time when looking at the wrong person in the wrong way was enough to send a man to the gulag, he wrote to Stalin saying that he was “ashamed to be called a Russian.” Nikolai Bukharin, who considered Pavlov indispensable, made the case for him: “I know that he does not sing the ‘Internationale,’ ” Bukharin wrote to Valerian Kuibyshev, the head of the state planning committee. “But . . . despite all his grumbling, ideologically (in his works, not in his speeches) he is working for us.”

Stalin agreed. Pavlov prospered even at the height of the Terror. By 1935-36, he was running three separate laboratories and overseeing the work of hundreds of scientists and technicians. He was permitted to collaborate with scholars in Europe and America. Still, his relationship with the government was never easy. Soviet leaders even engaged in a debate over whether to celebrate his eightieth birthday. “A new nonsensical letter from academician Pavlov,” Molotov wrote in the margin of a letter of complaint before it was passed to Stalin. Kuibyshev was deeply opposed to any state recognition. “Pavlov spits on the Soviets, declares himself an open enemy, yet Soviet power would for some reason honor him,” he grumbled. “Help him we must,” he said at the time, “but not honor him.” For a while, Kuibyshev prevailed, but in 1936, when Pavlov died, at eighty-six, a hundred thousand mourners, including Party officials, filed past his casket as he lay in state.

What Todes describes as Pavlov’s “grand quest”—to rely on saliva drops and carefully calibrated experiments to understand the mechanics of human psychology—lives on, in various forms. Classical conditioning remains a critical tool: it is widely used to treat psychiatric disorders, particularly phobias. But the greater pursuit is for a kind of unified field theory in which psychology and physiology—the subjective and the material realms—would finally be integrated.

And so we have entered the age of the brain. The United States and other countries have embarked upon brain-mapping initiatives, and Pavlov would have endorsed their principal goal: to create a dynamic picture of the brain that demonstrates, at the cellular level, how neural circuits interact. As Todes points out, while Pavlov examined saliva in his attempts to understand human psychology, today we use fMRIs in our heightened search for the function of every neuron. When he delivered his lectures on the “larger hemispheres of the brain,” Pavlov declared, “We will hope and patiently await the time when a precise and complete knowledge of our highest organ, the brain, will become our profound achievement and the main foundation of a durable human happiness.” We are still waiting, but less patiently than before. ♦

Michael Specter has been a staff writer at The New Yorker since 1998, and has written frequently about AIDS, T.B., and malaria in the developing world, as well as about agricultural biotechnology, avian influenza, the world’s diminishing freshwater resources, and synthetic biology.